The DEA confirmed on Thursday that earlier this year it seized two planes belonging to Starwood Management in Texas and Arizona. The agency declined to say why.

Rivera, who was born in the US, died at the peak of her career, when her plane nose-dived while flying from the northern-Mexican city of Monterrey early on Sunday. She was perhaps the most successful female singer in grupero, a male-dominated Mexico regional style, and had branched out into acting and reality television.

What caused the crash and why Rivera was on the plane remains unclear. The pilot and five other people were also killed.

A DEA spokeswoman, Lisa Webb Johnson, confirmed on Thursday that planes owned by Las Vegas-based Starwood Management were seized in Texas and Arizona, but she declined to discuss details of the case. The agency has subpoenaed all the company's records, including any correspondence it has had with a former Tijuana mayor who US law enforcement officials have long suspected has ties to organized crime.

The Mexican man widely believed to be behind the aviation company is an ex-convict named Christian Esquino, 50, who was not on the plane that crashed. Corporate records list his sister-in-law as the company's only officer, but insurance companies that cover some of the firm's planes say in court documents that the woman is merely a front and that Esquino is in charge.

Esquino pleaded guilty to a fraud charge that related to a major drug investigation in Florida in the early 1990s, serving about five months of a five-year prison sentence, and most recently was sentenced to two years in federal prison in a California aviation fraud case. He was deported upon release. Esquino and various companies he has either been involved with or owns have also been sued for failing to pay millions of dollars in loans, according to court records.

Jenni Rivera's brother, Pedro Rivera Jr, said that he didn't know anything about Esquino or why or how his sister had ended up in his plane.

Esquino told the Los Angeles Times in a telephone interview from Mexico City that the singer was considering buying the aircraft from Starwood for $250,000 and the flight was offered as a test ride. He disputed reports that he owns Starwood, maintaining that he was merely the company's operations manager "with the expertise".

In February this year, a Gulfstream G-1159A plane valued at $1.5m was seized by the US Marshals Service on behalf of the DEA, after it landed in Arizona on a flight that originated in Mexico.

Four months later, the DEA subpoenaed all of Starwood's records dating to 13 December 2007, including federal and state income tax documents, bank deposit information, records on all company assets and sales and the entity's relationship with Esquino and more than a dozen companies and individuals, including former Tijuana Mayor Jorge Hank-Rhon, a gambling mogul and a member of one of Mexico's most powerful families. US law enforcement officials have long suspected that Hank-Rhon is tied to organized crime but no allegations have been proven. He has consistently denied any criminal involvement.

The subpoena was obtained by the U-T San Diego newspaper. A Starwood attorney listed on the subpoena, Jeremy Schuster, declined to provide details. "We don't comment on matters involving clients," he said.

In September, the DEA seized another Starwood plane – a 1977 Hawker 700 worth $1m, after it landed in Texas from a flight from Mexico.

Insurers of both aircraft have since filed complaints in federal court in Nevada seeking to have the Starwood policies nullified, in part, because they say Esquino lied in the application process when he noted he had never been indicted on drug-related criminal charges. Both companies said they would not have issued the policies had he been truthful.

Another attorney for Starwood has not responded to phone and email messages seeking comment, and no one was at the address listed at its Las Vegas headquarters. The address is a post office box in a shipping and mailing store located between a tuxedo rental shop and a supermarket in a shopping center several miles west of the Las Vegas Strip.